JPH107286A - Sheet delivery mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet delivery mechanism hard to cause deterioration of quality of a picture image printed on a sheet. SOLUTION: A sheet 6 is delivered in an A direction and detected by a transmission type sensor 14, and a cam driving motor 23 for a pinch roller is rotated. Thereby, a cam 19 is rotated, vertical motion by this rotation is transmitted to a front side pinch roller 8 through a pressure spring 26, and pressurization is carried out. After the sheet 6 passes the transmission type sensor 15, the sheet 6 advances to an imaging starting position, a thermal head 27 is pressurized and imaging is started. When a sheet head end 6a is detected by the transmission type sensor 16, pressurization of a rear side pinch roller 11 is carried out as pressurization of the front side pinch roller 8. Though the sheet 6 is provided with moving force by the front and rear side driving rollers 7, 10 in this state, pressurization of the front side pinch roller 8 is released by rotating the cam driving motor 23 for the front side pinch roller simultaneously when a sheet rear end 6b passes the transmission type sensor 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper transport mechanism, and more particularly, to a paper transport mechanism of a printer, a copying machine, etc., which is suitable for use in a paper feed mechanism of a general printing machine or a transport mechanism of a read original such as a scanner. The present invention relates to a simple paper transport mechanism.

[0002]

2. Description of the Related Art A relatively thick print receiving paper, for example,
For paper reciprocating transport type printers that can print almost the entire area of a card (card) up to the end of the paper (card) for a plastic card with a thickness of 100 μm or more, etc. In order to minimize the image area, a drive roller for driving paper is provided before and after the opposing part of the thermal head and the platen roller for printing, and either or both drive rollers are provided. Must be moved while the card is held.

[0003] In the paper forward transport type printer according to the prior art, each pair of driving rollers is constituted by a driving roller and a pinch roller which is constantly pressed to rotate and is driven to rotate.

In order to reduce color misregistration during printing, the pressing force of a driving roller for holding the sheet is sufficiently increased to hold the sheet, that is, the sheet is received between the thermal head and the platen roller during printing. It is necessary to make the pressing force of the driving roller sufficiently larger than the acting force.

[0005]

However, as described above, when the pressure of the drive roller is increased, a large load resistance is applied at the moment when the leading edge of the sheet enters the nip portion of the drive roller, so that skew occurs. The print position may be misaligned every time, or a small difference in the amount of movement due to load fluctuation when paper enters or exits the nip may cause streak-like density differences in the printed image. And other problems.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object to provide a paper transport mechanism that does not easily deteriorate the quality of an image printed on paper.

[0007]

According to a first aspect of the present invention, there is provided a paper transport mechanism used in a printer or the like, comprising a drive roller for transporting a paper upstream and downstream of a thermal head. The paper transport mechanism is characterized in that a driving force for transporting the paper is alternately applied to the upstream and downstream drive rollers. ,
The paper transport mechanism has a pinch roller facing the drive roller, and a driving force for transporting the paper is given by pressing the pinch roller against the drive roller. According to a third aspect of the present invention, in the first or second aspect of the invention, the paper transport mechanism has a sensor for detecting an end of the paper or a mark attached to the paper, and the detection result of the sensor is provided. Wherein the driving force is applied to the upstream and downstream drive rollers based on the relationship between the pinch roller and the drive roller in the invention according to claim 2 or 3. The operation of pressing against the paper is performed by a cam mechanism, and when the leading edge of the paper enters the nip portion of the driving roller or the paper comes off from the nip portion. In which the sheet is kept free of large load fluctuations.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a structural view of a main part for explaining an embodiment of a paper transport mechanism according to the present invention.
Is a paper transport mechanism, 2 is a front (upstream) drive roller pair pressure unit, 3 is a thermal head pressure contact / release unit,
Is a rear side (downstream side) drive roller pair pressure unit, 5 is a paper feed roller, 6 is a sheet, 6a is a sheet leading end, 6b is a sheet trailing end,
7 is a front (upstream) drive roller, 8 is a front (upstream) pinch roller, 9 is a platen roller, 10 is a rear (downstream) drive roller, 11 is a rear (downstream) pinch roller,
12 is a paper drive motor, 13 is a drive belt, 14, 1
5, 16 are transmissive sensors, 17 is a reflection plate (light receiving unit),
18 is a guide roller, 19 is a cam, 20 is a shaft, 21
Is a position sensor plate, 22 is a sensor, 23 is a pinch roller cam drive motor, 24 is a link, 25 is a case,
6, a pressure spring; 27, a thermal head; 28, a cam drive motor for the thermal head;

In the embodiment shown in FIG. 1, the pinch rollers 8 and 11 are normally pressed against each other by a weak force enough to move the mass of the paper (or card body) 6, or are in a released state. I have. The sheet 6 is carried in the direction A, detected by the transmission sensor 14, the pinch roller cam drive motor 23 that presses the front pinch roller 8 against the front drive roller 7 rotates, and the cam 19 rotates. The vertical movement due to the rotation of the cam 19 is transmitted to the front pinch roller 8 via a pressure spring 26 for keeping the pressing force constant, whereby the front pinch roller 8 is pressed against the front drive roller. A DC motor or a pulse motor is used as the pinch roller cam drive motor 23. The instantaneous speed at the time of pressing the pinch roller is reduced, and the cam 19 is interposed to prevent a sudden pressure change. The rotary motion of the pinch roller cam drive motor 23 is converted into a vertical motion.

After the paper 6 has passed through the transmission type sensor 15, after a certain time (when the paper drive motor 12 is driven by a DC motor) or after applying a fixed number of pulses (when the paper drive motor 12 uses a pulse motor), the paper 6 Advances to the printing start position. After positioning at this point, the thermal head 27 is pressed and printing is started. For the pressure contact and release of the thermal head 27, the same configuration of the motor, cam, and spring mechanism for setting the pressing force is used as in the front drive roller-pressing unit 2.

When the transmission type sensor 16 detects the leading edge 6a of the sheet as the printing proceeds, the pressing of the rear pinch roller 11 is performed in the same manner as the pressing of the front pinch roller 8. In this state, the paper 6 has gained a moving force by the front and rear drive rollers 7 and 10, but further proceeds to the paper rear end 6.
At the same time as b passes through the transmission type sensor 14, the front pinch roller cam drive motor 23 is rotated to release the pressure of the front pinch roller 8. Also at this time, the moving force of the paper 6 is not applied in the moving direction of the sheet 6 since the moving is performed softly following the cam locus. From this state,
This time, the rear drive roller 10 takes the initiative in sheet conveyance.

The number of lines given to the thermal head 27 from the start point of printing is continuously counted by a counter (not shown). When the number of lines reaches a specified number corresponding to the sheet length, the sheet drive motor 12 Is stopped, and the thermal head 27 is once released. Then, when the paper drive motor 12 is rotated in the reverse direction and the rear end 6b of the paper is detected by the transmission sensor 14, the front pinch roller 8 is pressed. After 6a passes through the transmission sensor 16, the pressure of the rear pinch roller 11 is released.

The rear end 6b of the sheet is the transmission type sensor 1
After detecting a predetermined amount, the paper driving motor 1
2 is stopped to enter a waiting state for the next color printing. By repeating the above operation several times for the number of colors to be printed, a good quality color print can be obtained.

As a method of detecting the position of the sheet 6, in the embodiment shown in FIG. 1, the method of detecting the edge of the sheet using the transmission type sensor has been described. However, a reflection type sensor may be used. Alternatively, a mark code or the like may be printed at a position that does not affect the printing near the edge, for example, on the back side, instead of the edge of the sheet.

[0015]

According to a first aspect of the present invention, there is provided a sheet transport mechanism for use in a printer or the like, wherein the sheet transport mechanism has a driving roller for transporting a sheet upstream and downstream of a thermal head. The driving force for conveying the paper is alternately applied to the upstream and downstream driving rollers, and the invention according to claim 2 is the invention according to claim 1, wherein the paper conveying mechanism is configured such that the driving roller A driving force for conveying the sheet is provided by pressing the pinch roller against the driving roller, and the invention according to claim 3 or claim 2 In the present invention, the paper transport mechanism has a sensor for detecting an end of the paper or a mark attached to the paper, and based on a detection result of the sensor, The drive force is applied to the upstream and downstream drive rollers. According to a fourth aspect of the invention, in the second or third aspect, the operation of pressing the pinch roller against the drive roller is performed by a cam mechanism. By doing so, the sheet does not receive a large load resistance at the moment when the leading edge of the sheet enters the nip portion of the drive roller. A fine difference in the amount of movement due to load fluctuation when paper enters the nip or when paper comes off from the nip does not cause streak-like density differences in the printed image. Obtainable.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram for explaining an embodiment of a paper transport mechanism according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Paper conveyance mechanism, 2 ... Front side (upstream side) drive roller pair pressurizing unit, 3 ... Thermal head pressure contact / release unit,
4 rear-side (downstream) drive roller pair pressure unit, 5 paper feed roller, 6 paper, 6a paper end, 6b paper rear end, 7 front (upstream) drive roller, 8 front side ( Upstream) pinch roller, 9: platen roller, 10: rear (downstream) drive roller, 11: rear (downstream) pinch roller, 12: paper drive motor, 13: drive belt, 1
4, 15, 16: transmission type sensor, 17: reflection plate (light receiving portion), 18: guide roller, 19: cam, 20: shaft, 21: position sensor plate, 22: sensor, 23: cam drive motor for pinch roller , 24 ... link, 25 ... case, 26 ... pressure spring, 27 ... thermal head, 28 ...
Cam drive motor for thermal head, A: paper 6 loading direction.

Claims (4)

[Claims] 1. A paper transport mechanism used in a printer or the like, wherein the paper transport mechanism has a driving roller for transporting a paper upstream and downstream of a thermal head. Wherein the driving force is alternately applied to the upstream and downstream drive rollers. 2. The apparatus according to claim 1, wherein the sheet conveying mechanism has a pinch roller facing the driving roller, and a driving force for conveying the sheet is provided by pressing the pinch roller against the driving roller. The paper transport mechanism according to claim 1, wherein: 3. The paper transport mechanism has a sensor for detecting an end of the paper or a mark attached to the paper, and based on a detection result of the sensor, the upstream and downstream drive rollers apply 3. The paper transport mechanism according to claim 1, wherein a driving force is applied. 4. The paper transport mechanism according to claim 2, wherein the operation of pressing the pinch roller against the drive roller is performed by a cam mechanism.